Dengue fever is a viral infection which is transmitted via the bite of particular breeds of mosquito. It can cause severe flu-like symptoms and, sometimes, can be fatal.
There is no vaccination to protect against dengue fever or specific treatment for the disease, so preventing mosquito bites is the best form of protection.
Symptoms of dengue fever
Symptoms of dengue fever tend to develop within four to seven days of being bitten by the infective mosquito. It cannot be spread directly from person to person. The principal symptoms of dengue as detailed by the Center for Disease Control are:
High fever and at least two of the following:
- severe headache
- severe eye pain (behind eyes)
- joint pain
- muscle and/or bone pain
- mild bleeding manifestation (e.g., nose or gum bleed, petechiae, or easy bruising)
- low white cell count.
Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.
Watch for warning signs as temperature declines 3 to 7 days after symptoms began and the CDC advise to go immediately to a hospital or doctor if any of the following warning signs appear:
- severe abdominal pain or persistent vomiting
- red spots or patches on the skin
- bleeding from nose or gums
- vomiting blood
- black, tarry stools (faeces, or poos)
- drowsiness or irritability
- pale, cold, or clammy skin
- difficulty breathing.
Diagnosis of dengue fever
Doctors can usually diagnose dengue fever based on your history, being in a dengue risk area, physical examination and sometimes blood tests.
Dengue haemorrhagic fever (DHF) is a rare, severe and sometimes fatal form of dengue fever. It appears that people who have previously been infected with another strain of dengue fever are more at risk from this complication.
Initially, DHF presents in the same way as classical dengue fever, but after a few days the person’s condition worsens rapidly and he or she may develop one or more of the warning signs and symptoms listed above such as bruising, bleeding and drowsiness. It is important to get urgent medical treatment if these symptoms appear.
- Without treatment about 20% of people die from complications.
- With treatment by health professionals experienced in caring for people with the disease, this can be reduced to 1%.
- DHF is a leading cause of serious illness and death among children in some Asian countries.
There is no specific medical treatment for dengue fever. People are advised to rest, drink plenty of fluids and take paracetamol for pain.
Do not take aspirin and ibuprofen as these drugs might increase the risk of bleeding problems sometimes seen with dengue infections. Occasionally, people are admitted into hospital for observation and care.
Many people infected with dengue fever have only a mild illness and often are not even aware they have been infected. Sometimes recovery takes weeks to months and can be made more difficult by depression and fatigue.
Prevention of dengue fever
There is no vaccine to prevent dengue fever. It is spread by certain breeds of mosquito that carry the infection from human to human. The best way to avoid infection in areas where dengue-carrying mosquito populations are established, is to protect yourself against being bitten and reduce potential mosquito breeding sites.
To protect against mosquito bites:
- Wear loose-fitting, light-coloured clothing that covers up as much of the body as possible, especially around dawn and dusk when mosquitoes are usually most active.
- The dengue-carrying mosquito can be around during the day so keep covered, day and night.
- The mosquito that transmits dengue is commonly found in urban areas, so avoiding rural travel will not protect you against dengue.
- Use insect repellents containing either DEET, or icaridin (previously called picaridin).
- DEET should be of 30% concentration or more. Recently, up to 30% DEET has been approved for use in children over the age of two months.
- Use insect screens and mosquito nets.
- In parts of the world where both dengue fever and malaria occur, mosquito avoiding measures will need to be followed 24 hours a day.
Reduce mosquito breeding sites
Dengue-carrying mosquitoes generally breed in stagnant water found in man-made containers (eg, discarded tyres, uncovered barrels, buckets) rather than in rivers, swamps, open drains, creeks or mangroves.To eliminate breeding sites, empty any containers that hold water in and around the place you are staying.
Dengue spreading worldwide
Dengue fever was only found in a few countries prior to 1981. Since then, it has spread with the dengue carrying mosquito now established in over 100 tropical and sub-tropical countries. 40% of the world’s population is now at risk of contracting dengue fever. South-East Asia and the Western Pacific islands are two of the worst-hit areas.
The disease is particularly common in urban areas where standing water is near to homes and provides an ideal breeding ground for the carrier mosquitoes.
Countries often affected with dengue fever include:
- North Queensland, Australia
- Pacific Islands eg Fiji, Cook Islands, Marshall Is, Kiribati, New Caledonia
- Samoa, Tonga and Vanuatu
- Asia (including Cambodia, India)
- Latin/South America.
Dengue outbreaks can occur anywhere in tropical countries as shown in the map below, so if travelling, check the risk level before you go.
Get checked if unwell after travel
Anyone who is ill after returning from a dengue-prone area (or from overseas travel) should contact their GP so they can be assessed, get treatment where needed and be monitored for complications. It is advisable to phone your doctor's surgery before going in and tell them which countries you have travelled to, in case you have an infectious disease.
You can also phone Healthline, free (in NZ) on 0800 611 116 for advice. Healthline is staffed by registered nurses or other health professionals.
Learn more about dengue fever
Health topics – dengue World Health Organisation
Health map reports – Dengue fever locations last 3 months Center for Disease Control and Prevention (USA)
Travel advice Safe Travel (NZ)